Nickel metal hydride testing

Eric_Cable · #1 05-09-2003, 01:50 PM

Greetings all,

A couple of years ago I discovered Nimh AA batteries for all of my flashes and film cameras. I ended up putting them in everything, so total I have about 60 of them. In the time I have had them I have recharged them around 100 times, no where near the life expectancy of 500 times. The chargers I bought for these batteries were the recomended charger from Radio Shack, which was also where I bought the batteries. Well, I think I shouldn't have done that, as the charger is not extremely smart. It is a fast charger, but it doesn't shut off the cells individually when they reach full charge. So, some of the cells may get charged more than others depending on their state of discharge. End result, they can get pretty hot while charging. I think this may be a bad thing. At a job last week, three of my four f100s showed a low battery indicator after less than 5 rolls each. This has never before happened, not even on one body, let alone three. Usually I shoot 30 rolls between the four bodies, never a low batt. Ok, so I have a bad cell or cells. Since each camera holds 6 cells, I am thinking maybe not all 6 are bad. I just went to Fry's and bought 24 new batteries and two new chargers. I can easily see after using them that these chargers are much smarter, as the batteries don't get hot. Question is: is there a way to test the NimH cells to find out which are bad and which are ok? I can't take the chance of using questionable cells in a camera, but I have 11 speedlights, Pocket Wizards, Light meters, etc. that I can use them in, not to mention just to have as backup batteries. But I don't want to keep any if I can't confirm the good cells.

Thanks!

Eric Cable

www.profilephoto.com

Adam Wade · #2 05-09-2003, 03:31 PM

I use one of the best compact AA chargers out there, the Maha MH-C204F, and my batteries always get hot. Frankly, I'm not sure I've used a charger where they don't. I suppose there may be an advantage to a charger that uses a closed loop with a thermocouple, but if so, I have yet to hear anything solid about it.

One of the keys to keeping NiMH batteries healthy is cycling them 3 full times when new, and tehn cycling them once every 10 charges or so. Did you run any refresh cycles on those batteries you have been using for some time? A few refresh cycles might bring them back to life for you.

Eric_Cable · #3 05-09-2003, 06:05 PM

How hot is hot? I am talking about hot like I don't want to hold onto them to tight because it will become painful. Not hot like raise a welt hot, but hotter than warm. The new charger doesn't get them hot at all, barely even warm.

As for refresh, that occured to me, but I haven't seen a charger with a refresh cycle. Does yours have one? Without a refresh cycle, I suppose I could put them in a battery tray and put a lamp accross the teminals to take them down. However, then they will end up totally dead, and the charger won't sense any voltage when they are put into the charger.

Eric

creator · #4 05-09-2003, 10:22 PM

get powerex 2200

http://shop.mahaenergy.com/store/comersus_Index.asp

Adam Wade · #5 05-10-2003, 11:16 PM

[ QUOTE ]
How hot is hot? I am talking about hot like I don't want to hold onto them to tight because it will become painful. Not hot like raise a welt hot, but hotter than warm. The new charger doesn't get them hot at all, barely even warm.

[/ QUOTE ]
Yeah, the "hot" you describe sounds like what I get with the Maha. SOME types of batteries can have their life severely shortened if they are not kept below a certain temperature, and some manufacturers are simply concerned about warpage and damage to the plastic cases housing the batteries. I've been using NiMH AA batteries for about 5 years now, and I own about 100 various cells of various ages, and I don't see where older batteries that were charged with the Maha and held to the regimen suggested by Thomas Distributing are holding any less of a charge than brand-new ones that were conditioned thrice. Then again, I dont' spend a lot of time measuring the differences, so they may have declined, but not a lot, if you follow what I'm saying.

[ QUOTE ]
As for refresh, that occured to me, but I haven't seen a charger with a refresh cycle. Does yours have one?

[/ QUOTE ]
Yes, the Maha one does, and after having seen the difference between batteries that were never cycled and ones that were cycled 3 times, I'll never buy another one for NiMH batteries that hasn't got refresh cycle capacity.

[ QUOTE ]
Without a refresh cycle, I suppose I could put them in a battery tray and put a lamp accross the teminals to take them down. However, then they will end up totally dead, and the charger won't sense any voltage when they are put into the charger.

[/ QUOTE ]
I've been told the "target" voltage is 1v for a AA NiMH to end a refresh cycle and begin to charge. You should be able to get there with a bulb, and simply remove it from the rig once the battery dimmed sufficiently, but that requires more attention than I want to spend on batteries.

The Maha units are small, affordable, and microprocessor-driven. They weigh almost nothing; one Maha charger with AC and cigarette lighter 12v adapters is a standard part of my road kit.

"creator", The Powerex batteries are alos excellent. I've always bought from Thomas Distributing, simply because they are the B&H of batteries; reliable advice, great customer service, usually in-stock, and they still have great prices.

Here is the C204F; it charges AAs in pairs, and has separate circuits for each pair; you can charge one set while you condition another, or what have you. It'll also condition and charge NiCDs if you have any left.

http://thomas-distributing.com/maha-mh-c204f.htm

They also have a "cool" charger version now:

http://thomas-distributing.com/mhc401fs.htm

The literature DOES say they will take more charge if they are kept cool while charging, so I guess I've learned something new today.

They also have some kind of nifty testing circuitry that can accurately assess the battery's ability to take more charge. It also runs each battery individually instead of in pairs, like the C204F. There is about a 50% premium in price for the C401FS. If I get another charger at some point, I'll probably grab one of the new ones.

#6 05-14-2003, 09:41 PM

I have a maha charger and I found if you keep the lid off and you have your charger in an area where there is a cool breeze, ( window cill, air condintioner vent ect.. ) you will find you batteries are very happy.
If you test the voltage right out of the charger you will also find they will be higher when charged "cool". Don't get hung up on the voltage as it dropps off out of the charger. I made these conclusions from having a maha charger that does 2 way batteries, it has a little wire with a magnet on it that monitors heat. And the second source was from a battery store, not the kind in a mall but from a place that has everything from aaa to batteries the size of skids for backups in operataing rooms.

I have batteries ( nicads ) that are ten years old and still working as well as nic md hid.

Barry

Eric_Cable · #7 05-15-2003, 12:57 PM

Thanks all for the advice! I have ended up putting all of my batteries through a home-made refresh cycle, three times each. In other words, a light bulb. My bathroom is a mess, 100 or so cells sitting around in various states of discharge/recharge, and a warm glow from mini-incadescent bulbs. The cool chargers that I have (lenmar) really are cool, and I find it quite fascinating that they charge fully discharged cells just as fast as my old "hot" charger, but the Lenmars are totally cool. Barely even a hint of warmth. After I put these all through their three discharge cycles, I think my discharge days will be over, it is too much effort to do more than once!

Eric